Analysis of Technologies and Designs of the EAF as an Aggregate for Heating and Melting of Scrap

Abstract

The following issues are considered: the role of hot heel in scrap melting by electric arcs in the furnace freeboard; advantages and disadvantages of furnaces with a single charging and those with a telescoping shell; Specifics of furnace scrap hampering its heating by burners. The possibilities of using different types of burners for scrap heating are analyzed including stationary burners and jet modules as well as slag door, oriel, and roof rotary burners. The data of industrial tests of the process of two-stage melting of scrap in different EAFs with the use of rotary burners without using electrical power in the first stage are given. Under conditions of short tap-to-tap times in modern EAFs the high-temperature scrap heating by burners is impossible. The advantages and disadvantages of EAFs of various types with preheating of scrap with off-gases and melting of heated scrap in liquid metal, including both Consteel conveyer furnaces and shaft furnaces of the Quantum, SHARC, COSS, ECOARC types are considered. In all the shaft furnaces, the scrap preheating temperatures do not exceed 400–450 ℃ and electrical energy consumption is about the same equal to 300 ± 15 kWh/t. This is explained by the fact that the possibilities of further raising the scrap preheating temperature with off-gases and thereby reducing the consumption of electrical energy are practically exhausted.